View Full Version : Problem with pins 30/31?

01-25-2008, 06:21 AM
I have an SD Card that works on my other breadboard prop. The breadboard version is on pins 16-19 and works fine. I've changed the pin layout up a little bit due to physical constraints, and soldered the molex SD socket to the protoboard now. I'm now using the following pins for the socket:
Data Out:··· 30
Data In:····· 0
Clock:········ 31
Chip Select: 1

I beleive pins 30 and 31 are used for the eeprom, and I think there may be a conflict going on which is giving me an error when I try to load a volume from the SD. Any thoughts?

Mike Green
01-25-2008, 06:40 AM
Pins 30 and 31 are used to communicate with a PC. Pins 28 and 29 are used for the EEPROM. The problem you're running into is that 31 is receive (from the PC) and 30 is transmit (to the PC) and there's a conflict with whatever you have connected there (MAX3232 or FT232R or whatever).

01-25-2008, 06:50 AM
Do you suggest I re-route the 30/31 pins to elsewhere?

01-25-2008, 07:29 AM
FYI for future people with the same problem... I swapped pins 31/30 with 2/1 so I'm now using pins 0-3 and the card works now. Pretty nice setup too. The card is in a corner of the board out of the way, with only two hookup wires. The rest is soldered directly to vdd, vss, pins 0 and 1. Thanks guys.

Mike Green
01-25-2008, 07:40 AM
The problem is that the I2C EEPROM could interact with the data going back and forth to the SD card and vice versa. You might be able to use pin 30 for both data in (to the SD card) and transmit to the PC and use pin 29 for the SD card clock pin, then use pins 0 and 1 for chip select and data out (from the SD card). That way, whenever chip select is false, there'd be no interaction with the other SD card pins, yet data transferred from/to the SD card wouldn't affect the EEPROM since the clock (SCL) would be inactive. There would be data going to the PC, but that shouldn't affect anything.